With the Cooley Spruce gall adelgids, the immature female overwinters and maturesin the spring. She lays several hundred eggs on side branches. After the eggs hatch, the young migrate to the base of needles on the new growth. The feeding induces the plant to envelope the individual adelgids as a group, thus forming a gall. By late June to July, the adelgids emerge from the galls. The females become winged and fly to Douglas fir or other spruces. Several life cycles later, and through most of another growing season, the adelgids return to the spruce trees. It takes two full growing seasons for the adelgids to make one complete cycle between both hosts.
The Eastern spruce gall adelgids overwinter as immature females, the females mature in the spring and lay between 100 and 200 eggs next to buds ready to open. The young feed on needles and eventually move to the base of the needles. A gall develops. After leaving the galls in late June to early July, the Eastern spruce gall adelgids become mature flying females. She lays her eggs in unprotected masses near the tips of needles. The cycle then starts again.